Continuous polymer synthesizer

ABSTRACT

Described is a system and method for synthesizing polymeric molecules such as oligonucleotides and polypeptides. The system is capable of continuously synthesizing molecules by providing an array of reaction sites and an array of stations for carrying out synthetic manipulations. The reaction sites in the former array can be placed in a fixed order and at fixed intervals relative to each other. Similarly, the stations can be placed in a fixed order and at fixed intervals relative to each other. The two arrays can be moved relative to each other such that the stations carry out desired steps of a reaction scheme at each reaction site. The relative locations of the stations and the schedule for the relative movement can correlate with the order and duration of reaction steps in the reaction scheme such that once a reaction site has completed a cycle of interacting with the full array of stations then the reaction scheme is complete.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/521,573, filed on Sep. 13, 2006 which claims priority under 35 U.S.C.§119(e) to U.S. Provisional Application No. 60/717,376 filed Sep. 14,2005, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present embodiments relates to systems and methods for synthesizingmolecules such as polymers. More specifically, the present embodimentsrelate to devices and methods for continuously synthesizing biologicalpolymers such as polypeptides and oligonucleotides.

2. Description of the Related Art

Oligonucleotides are among the most important and prevalent reagentsused in biotechnology laboratories engaged in research, diagnostics andtherapeutics. The high demand for oligonucleotides derives from theirexquisite specificity for complementary nucleotide sequences in DNA orRNA obtained from biological samples. This specificity allowsoligonucleotides to be used as probes that specifically bind to uniquesequences present in less than part-per-billion abundance in a complexbiological milieu. This specificity can be used in order to provide adiagnosis for an individual at risk for a particular disease based onthe presence or absence of a gene sequence known to be associated withthe disease. Furthermore, this specificity also forms the basis for useof oligonucleotides as reagents for synthesizing molecules of DNA or RNAhaving a particular nucleotide sequence of interest. For example, a genesequence associated with a particular disease can be cloned by bindingone or more oligonucleotides to the gene sequence and then performing anamplification reaction on the bound complex to make multiple copies ofthe sequence. The cloned gene sequence can subsequently be utilized forresearch into the disease or can even be used for therapeutic treatmentof individuals afflicted with the disease.

Oligonucleotide synthesis is a cyclical process that assembles a chainof nucleotides. Nucleotides are added one by one through a cycle ofchemical reactions, in which a particular molecule (e.g., a nucleotide)is added to a growing DNA molecule (e.g., a growing DNA chain),sometimes via catalysis, until the desired chain is complete. Generally,each cycle of chemical reactions includes the steps of detritylation,coupling, capping and oxidation. During the detritylation or“deprotection” step, a dimethoxytrityl (DMT) group is removed from thelast nucleotide of the growing DNA chain to allow the addition of thenext nucleotide. The amount of DMT released from each cycle is monitoredto determine coupling efficiency. The release of DMT is apparent becausea bright orange color is emitted as DMT is released.

Similar synthetic methods can be used to produce oligonucleotides at avariety of throughputs to satisfy demands spanning those of smalllaboratories to large manufacturing facilities. The methods themselvesare relatively robust being capable of handling oligonucleotides ofvarying length from just a few nucleotides per molecule to over 100nucleotides per molecule. Furthermore, the methods are capable ofproducing oligonucleotides having a myriad number of differentsequences, the complexity of which is illustrated by the fact that thenumber of different decamers (molecules having 10 nucleotides) that canbe made using just the 4 common DNA nucleotides (A, T, C and G) is4¹⁰=1,048,576.

Typically, large manufacturing facilities achieve high throughput byemploying a large number of synthesizers that are similar to those usedin smaller laboratories. These synthesizers are typically configured toperform individual steps of the monomer addition cycle in succession,and can do so for several different oligonucleotides in parallel. Thus,the sequence of reactions for a plurality of oligonucleotides isperformed in order such that detritylation is carried out for eacholigonucleotide, then coupling is carried out for each oligonucleotide,followed by capping of each oligonucleotide followed by oxidation ofeach oligonucleotide. The cycle is then repeated until full lengtholigonucleotides are obtained.

Although a large number of such synthesizers can be employed to achieverelatively high throughput, this scale-up approach can result inunwanted inefficiencies. An example of such inefficiency is the timethat each synthesizer sits idle while waiting for individual incubationsteps to be completed prior to delivery of the next reagent to any ofthe reactions. Furthermore, instruments can experience substantial downtime between synthesis reactions when new reaction vessels or reagentsare reloaded.

What is needed are synthetic methods and devices that allow parallelsynthesis of oligonucleotides and other molecules such that a pluralityof reactions can be carried out and monitored without interruption. Thepresent embodiments satisfy this need and provides other advantages aswell.

SUMMARY OF THE INVENTION

The present embodiments provide a system for continuously synthesizingmolecules, whereby the molecules are synthesized by performingsequential steps of a reaction. The system can include (a) a stageconfigured to accept an array of reaction sites; (b) an array ofstations including (i) reagent dispensing stations configured toseparately and sequentially provide synthesis reaction solutions to aplurality of the reaction sites for the sequential steps, and (ii)imaging stations configured to obtain images of at least one of theplurality of reaction sites; and (c) a control system configured to movethe stage or the array of stations so that the plurality of reactionsites sequentially communicate with at least one of the dispensingstations and at least one of the imaging stations, and wherein thecontrol system is further configured to allow replacement of a firstreaction site from the array of reaction sites with a second reactionsite while the system continuously synthesizes molecules at otherreaction sites of the plurality of reaction sites.

Further embodiments provide system for continuously synthesizingmolecules, comprising: (a) a stage comprising a plurality of reactionsites in a fixed order and at fixed distances from one another, (b) aplurality of dispensing stations configured to deliver reagents to saidreaction sites to start a reaction, wherein said dispensing stations arelocated along said stage at fixed distances from one other; and (c) acontrol system configured to sequentially dispense said reagents intosaid reaction sites on a predetermined schedule so that a first reactionin a reaction site is completed before a second reaction in saidreaction site is initiated and wherein said distances and said schedulecorrelate to the order and the duration of steps required to completesaid reaction.

The present embodiments further provide a method of continuouslysynthesizing molecules, whereby the molecules are synthesized byperforming sequential steps of a reaction. The method can include thesteps of (a) providing a stage including an array of reaction sites; (b)sequentially providing synthesis reaction solutions to a plurality ofthe reaction sites from reagent dispensing stations configured toseparately and sequentially provide synthesis reaction solutions to thereaction sites for the sequential steps; (c) sequentially obtainingimages of at least one of the plurality of reaction sites at imagingstations; and (d) replacing a first reaction site from the array ofreaction sites with a second reaction site while the system continuouslysynthesizes molecules at other reaction sites of the plurality ofreaction sites.

Further embodiments provide a system for continuously synthesizingmolecules, comprising (a) a stage comprising a plurality of reactionsites in a fixed order and at fixed distances from one another, (b) aplurality of dispensing stations configured to deliver reagents to saidreaction sites to start a reaction, wherein said dispensing stations arelocated along said stage at a fixed distances from one other and whereinsaid distances correlate to the time required to complete said reaction;and (c) means for sequentially dispensing said reagents into saidreaction sites on a predetermined schedule so that a first reaction in areaction site is completed before a second reaction in said reactionsite is initiated and wherein said distances and said schedule correlateto the order and the duration of steps required to complete saidreaction.

Also provided is a system for continuously synthesizing polymers,whereby monomers are added to a growing polymer by repeating sequentialsteps of a reaction. The system can include (a) a stage including anarray of modules, the modules configured to accept an array of reactionsites in a fixed order and at fixed intervals; (b) an array of stationsfor performing the sequential steps, including (i) dispensing stationsconfigured to provide synthesis reaction solutions for the sequentialsteps to a plurality of the reaction sites, and (ii) imaging stationsconfigured to obtain images of at least one of the plurality of reactionsites; (c) at least one solution removal device configured to remove thesynthesis reaction solutions from the plurality of reaction sites,wherein the relative locations of the stations are fixed with respect tothe array of stations; and (d) a control system configured to move thearray of modules or the array of stations on a schedule for sequentialcommunication of the plurality of reaction sites with the stations andremoval of the solutions by the at least one solution removal device,wherein the relative locations of the stations and the schedulecorrelate with the order and duration of the sequential steps of thereaction.

The present embodiments also provide a method for continuouslysynthesizing molecules, comprising (a) providing a stage comprising aplurality of reaction sites in a fixed order and at fixed distances fromone another, (b) providing a plurality of dispensing stations configuredto deliver reagents to said reaction sites to start a reaction, whereinsaid dispensing stations are located along said stage at a fixeddistances from one other and wherein said distances correlate to thetime required to complete said reaction; and (c) sequentially dispensingsaid reagents into said reaction sites on a predetermined schedule sothat a first reaction in a reaction site is completed before a secondreaction in said reaction site is initiated, and wherein said distancesand said schedule correlate to the order and the duration of stepsrequired to complete said reaction.

Further provided is a method of continuously synthesizing polymers,whereby monomers are added to a growing polymer by repeating sequentialsteps of a reaction. The method can include the steps of (a) providing astage including an array of reaction sites, wherein the reaction sitesare placed in a fixed order and at fixed intervals; (b) providing anarray of stations for performing the sequential steps, including (i)dispensing stations configured to provide synthesis reaction solutionsfor the sequential steps to a plurality of the reaction sites, and (ii)imaging stations configured to obtain images of at least one of theplurality of reaction sites; (c) providing at least one solution removaldevice configured to remove the synthesis reaction solutions from theplurality of reaction sites, wherein the relative locations of thestations are fixed with respect to the array of stations; and (d) movingthe array of reaction sites or the array of stations on a schedule forsequential communication of the plurality of reaction sites with thestations and removal of the solutions by the at least one solutionremoval device, wherein the relative locations of the stations and theschedule correlate with the order and duration of the sequential stepsof the reaction.

The present embodiments further provide a method of continuouslysynthesizing polymers, whereby monomers are added to a growing polymerby repeating sequential steps of a reaction. The method can include thesteps of (a) providing a circular table including an array of modules,the modules configured to accept an array of multi-well plates in afixed order and at fixed intervals along a circular path; (b) rotatingthe circular table such that each multi-well plate of the array ofmulti-well plates sequentially communicates with an array of stations inorder of (i) providing deblock reagent to the multi-well plate at adeblock reagent dispensing station, (ii) removing the deblock reagentfrom the multi-well plate at a deblock reagent removal station after apredefined time interval from the adding deblock reagent, (iii)providing monomer reagent to the multi-well plate at a monomer reagentdispensing station, (iv) removing the monomer reagent from themulti-well plate at a base reagent removal station after a predefinedtime interval from the adding monomer reagent, (vii) providing capreagent to the multi-well plate at a cap reagent dispensing station, and(viii) removing the cap reagent from the multi-well plate at a capreagent removal station after a predefined time interval from the addingcap reagent, wherein the dispensing stations are configured as an arrayof stations in a fixed spatial relationship corresponding to the orderof the sequential steps of the reaction; performing repetitions of step(b) for each of a first, second and third multi-well plate, wherein thesecond multi-well plate is unloaded from a first module and the thirdmulti-well plate is loaded to the first module while the systemcontinuously synthesizes polymers at the first multi-well plate, whereinat least one of the repetitions for the first multi-well plate occurssimultaneously with at least one of the repetitions for the secondmulti-well plate, and wherein at least one of the repetitions for thefirst multi-well plate occurs simultaneously with at least one of therepetitions for the third multi-well plate.

Also provided is a system for continuously synthesizing polymers,whereby monomers are added to a growing polymer by repeating sequentialsteps of a reaction. The system can include a stage including an arrayof multi-well plates, wherein the multi-well plates are placed in afixed order and at fixed intervals along a circular path; an array ofdispensing stations configured to provide synthesis reaction solutionsfor the steps to the multi-well plates, wherein the relative locationsof the dispensing stations are in a fixed spatial relationshipcorresponding to the order of the sequential steps; and a control systemconfigured to move the array of dispensing stations or the array ofmulti-well plates and to actuate the dispensing stations, wherein thedispensing stations dispense solutions to the multi-well plates whilethe array of dispensing stations or the array of multi-well plates ismoving.

The present embodiments further provide a method of continuouslysynthesizing polymers, whereby monomers are added to a growing polymerby repeating sequential steps of a reaction. The method can include thesteps of providing a stage including an array of multi-well plates,wherein the multi-well plates are placed in a fixed order and at fixedintervals along a circular path; providing an array of dispensingstations configured to provide synthesis reaction solutions for thesteps to the multi-well plates, wherein the relative locations of thedispensing stations are in a fixed spatial relationship corresponding tothe order of the sequential steps; moving the array of dispensingstations or the array of multi-well plates; and dispensing reactionsolutions for the sequential steps of the reaction from the dispensingstations while the array of dispensing stations or the array ofmulti-well plates is moving.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of a continuousoligonucleotide synthesizer.

FIG. 2 is a schematic diagram of the array of stations within thecontinuous oligonucleotide synthesizer of FIG. 1.

FIG. 3 is a block diagram of one embodiment of a system for continuouslysynthesizing polymeric molecules.

FIG. 4 is a flow diagram of one embodiment of a method for synthesizingoligonucleotides.

FIG. 5A is a perspective view of one embodiment of a plate module andits associated plate holder that are configured to be used within thecontinuous oligonucleotide synthesizer of FIG. 1.

FIG. 5B is a perspective view of one embodiment of the plate holderillustrated in FIG. 5A.

FIG. 5C is a perspective view of the bottom of the plate holder shown inFIG. 5B.

FIG. 5D is a perspective view of the plate module shown in FIG. 5A.

FIG. 5E is a cross-sectional view of a plate holder mounted onto a platemodule taken across the line 5E-5E of FIG. 5A.

FIG. 6 is a top-view image of a microtiter plate that is used within theplate holder of FIG. 5B.

FIG. 7 is a schematic diagram of one embodiment of a system fordispensing reaction solutions within a continuous polymer synthesizer.

FIG. 8 is a schematic diagram of one embodiment of the trajectory of amicrotiter plate passing under a dispenser nozzle that delivers reactionsolutions into the microtiter plate.

FIG. 9 is a flow diagram of one embodiment of a method for dispensingreagents into a microtiter plate within a continuous polymersynthesizer.

FIG. 10 shows a screen shot of a user interface for constructing andmodifying a firing table.

FIG. 11 shows a circuit diagram for a hardware abstraction layer usefulfor controlling a fluid dispenser.

DETAILED DESCRIPTION

Some embodiments relate to a system for continuously synthesizing aplurality of different molecules, such as polymeric molecules. Systemsof the embodiments can be configured to include an array of reactionsites and an array of stations for carrying out synthetic manipulations.The reaction sites in the array can be placed in a fixed order and atfixed intervals relative to each other. For example, an array ofmicrotiter plates can be placed along the outer edge of a circulartable. Each reaction site (i.e. well) can be assigned a different targetproduct compared to the products to be synthesized at other reactionsites in the array. Similarly, the stations can be placed in a fixedorder and at fixed intervals relative to each other. For example, thestations can be placed in a circular array having a perimeter thatcorresponds to the layout for the array of microtiter plates. Each ofthe stations can be configured to carry out a different manipulationcompared to other stations in the array. The two arrays can be movedrelative to each other such that the stations carry out desired steps ofa reaction scheme at each reaction site. The relative locations of thestations and the schedule for the relative movement can correlate withthe order and duration of reaction steps in the reaction scheme suchthat once a reaction site has completed a cycle of interacting with thefull array of stations then the reaction scheme is complete. Forexample, oligonucleotides contained in microtiter plates on the circulartable can each be extended by addition of a single nucleotide if theorder of the stations, spacing between the stations and rate of passagefor each plate corresponds to the order of reagent delivery and reactiontime for a complete monomer addition reaction cycle.

In accordance with the configuration set forth above, and described infurther detail below, each lap (or full revolution in embodiments wherea circular table is used) completed by an individual reaction site cancorrespond to addition of a single nucleotide to the growingoligonucleotide chain. Furthermore, several reaction sites present in anarray of reaction sites concurrently move along similar, repeated lapsthrough the system, thereby resulting in continuous synthesis by thesystem. Using a system or method of the embodiments, reagents can beactively delivered or removed from a first reaction site in accordancewith a first reaction step while incubation, or some other reactionstep, occurs at a second reaction site. (The identifiers “first” and“second” are used throughout this disclosure for purposes ofdistinguishing two nouns and, unless indicated otherwise, are notintended to denote a spatial or temporal order) Thus, an array ofstations can be configured in a spatial and temporal relationship withan array of reaction sites such that reactions occur at multiplereaction sites concurrently even as the reaction sites are subjected todifferent steps of the reaction at any given time, thereby allowingcontinuous and simultaneous reactions to be performed.

Some embodiments provide a system that is configured to allowreplacement of a first reaction site with a second reaction site whilethe system continuously synthesizes molecules at a third reaction site.Thus, a first reaction site (or matrix of reaction sites, such as amicrotiter plate) can be individually added or removed from the systemwithout interrupting synthesis reactions occurring at another reactionsite (or matrix of reaction sites), thereby providing the advantage ofcontinuous synthesis for the array of reaction sites. A furtheradvantage is that polymers of different lengths can be synthesizedcontinuously and simultaneously in the array of reaction sites becausereaction sites for each of the different polymers can complete adifferent number of laps through the system and the reaction sites canbe removed or added to the system in an independent fashion such thatreactions occurring at other sites are not perturbed.

In one embodiment, the system includes a circular plate that isconfigured to hold a plurality of reaction sites along its outer edge.Distributed around the outer edge of the circular plate are also aseries of stations, where each station is configured to take aparticular action relating to the polymer synthesis process. As thecircular plate rotates, reaction sites move in a circular pattern alongthe outer edge of the plate. The stations located around the outerperimeter are placed so that each station can act upon the reactionplates as they pass below the station. In one embodiment, the reactionsite passes under a station configured to dispense a reaction solutionto the reaction site. A computer control system is programmed todetermine the proper solution to dispense within each reaction site, andto coordinate the movement of the circular plate with the position ofthe station. Other stations within the device are configured to gatherimages of the reaction sites or to add or remove reaction sites.

A synthesizer of the present embodiments can be configured forcalibrated solution delivery. An array of reaction sites, such as anarray of multiwell plates, can be attached to a rigid carrier such as acircular table or other stage. The carrier is typically sufficientlyrigid that the location of each reaction site relative to others in thearray does not change substantially during the course of typicalsynthesizer operation. An optical sensor can be placed at each of thedispensing stations allowing the positions of the multi-well plate onthe rigid carrier to be determined for each of the dispensers. Thisallows multi-well plate-specific optimization of the dispense timingthereby compensating for positional tolerances of the dispensersrelative to the reaction sites. For example, the position of eachmulti-well plate on a circular table can be determined such that timingof dispenser firing can be correlated with rotation of the plate foraccurate delivery of reagents to the individual wells. So long as therelative positions of the reaction sites are not substantially altered,calibration is only required following assembly of the synthesizer, oneor more of its dispensing stations, or the rigid carrier. In addition,the learned position data can be saved to a file and does not need to bechanged unless some disassembly of the machine occurs.

As will be described in detail below, embodiments of the system providefor dispensing reaction solutions as an array of reaction sites ismoving. For example, as a reaction site approaches a reaction station,the computer control system determines the proper time to dispense thereaction solution, and then instructs the dispensing station to dispensethe solution at the proper moment the reaction site is passing below adispensing valve within the dispensing station. Of course, it should berealized that a dispensing station may be configured to dispense aplurality of solutions from separate valves to a plurality of movingreaction sites. For example, the reaction sites may be wells of aconventional microtiter plate, and the dispensing station may beconfigured to dispense reaction solutions to the wells of an entire rowor column of the microtiter plate at the same time or in fastsuccession. In particular embodiments, a linear arrangement of valvescan be instructed by the computer control system to dispense reagentssequentially and in a way that coincides with the arcuate trajectory ofthe microtiter plate.

A synthesizer of the present embodiments can further include dispensingnozzles having localized reservoirs. Reagents for a synthetic reactioncan be maintained in large storage tanks that are in fluid contact withappropriate dispensing nozzles. The local reservoirs allow rapiddelivery of reagents and replacement of bulk reagents in the largestorage tanks during the course of continuous synthesis.

Another embodiment relates to an imaging system that is configured totake a digital image of reaction sites after a reaction solution hasbeen dispensed or removed, and then process that image to determine ifreaction solutions were dispensed to or removed from the appropriatesites. If a quality control module within the system determines that aparticular site did not properly receive or evacuate a reactionsolution, it can be marked with an error flag to indicate that furthersteps of the reaction at that site should be discontinued or that thereaction site should be removed from the system. An advantage of theimaging stations is that they can provide real-time confirmation thatthe upstream dispensers are functional and that evacuation of the plateswas successful, resulting in the ability to pause the synthesis cycleand conduct maintenance without sacrificing downstream reactions.

In one embodiment, the system includes a series of dispensing stationsaround the circumference of the device, and proximal to one or more ofthe dispensing stations is a digital camera that is configured to takean image of the reaction sites after a reaction solution has beendispensed into the reaction vessel.

It should be realized that not every reaction site need receive areaction solution at every reaction station. Thus, the imaging system ispreferably programmed to determine whether a particular reaction sitewas supposed to have received a reaction solution, and if so, thendetermine if the reaction site has such a solution within the vessel.

A system of the present embodiments can further include a continuouslyavailable solution removal device. Thus, removal of reaction solutionsneed not be confined to occurring only at a particular station. Ratherremoval of a reaction solution can occur at any time during a syntheticreaction sequence or at any location along a path traversed by areaction site in a system of the present embodiments. In particularembodiments, a valve attenuated vacuum evacuation device is available toindividual multi-well plates in an array of multi-well plates at alltimes during a synthetic reaction.

A system of the present embodiments can further include a gas knife forproviding a flow of inert gas over the reaction sites. In particularembodiments, the gas knife can be maintained over each site at all timesduring a synthesis reaction. A device can be used to supply arectangular jet of inert gas, either laminar or turbulent, that is blowntangentially over the upper surface of a multi-well plate or otherreaction site. The device can be further configured such that the gasknife travels with each of the multiwell plates as they move along asynthesis path. A gas knife can provide the advantage of reducingcontamination between reaction sites by removing volatile reagents orsolvents that have entered the vapor phase. It can also protect eachreaction site from unwanted vapors generated by dispense stations.

In one embodiment, a system provided by the present embodiments includesan oligonucleotide synthesizer having a circular array of reactionsites. In this embodiment, each time the array of reaction sitescompletes a rotation, one nucleotide base is added to theoligonucleotide at each site. In this embodiment, there may be aplurality of reaction solution dispensing stations, wherein a firststation dispenses adenosine, a second station dispenses thymidine, athird station dispenses cytidine and a fourth station dispensesguanosine. In addition, other dispensing stations located along theouter perimeter of the circular array can be configured to dispenseother reaction solutions that are necessary in order to synthesizeoligonucleotides. For example, the dispensing stations can dispensereaction solutions for detrytilation, coupling, capping and oxidation,in accordance with the steps for synthesizing an oligonucleotide chain.

Other embodiments provide a system that synthesizes other polymericmolecules. For example, the synthesizer can be configured to dispensereaction solutions that will synthesize polypeptides. The process ofpeptide synthesis on solid supports generally involves building apeptide from the carboxyl-terminal end. The peptide is attached to asolid support via its carboxy-terminal amino acid and further includes aprotecting group on the amino-terminal α-amino group. The protectinggroup is then cleaved off of the peptide to form a deprotected peptide.Next a monomeric amino acid, also containing an α-amino protectinggroup, is contacted with the de-protected peptide under conditions forformation of a peptide bond between the α-amino group of the deprotectedpeptide and the α-carboxy group the monomeric amino acid. The monomericamino acid can be provided in an activated form or an activating reagentcan be added to the amino acid and growing peptide. Washes can becarried out between steps to remove reagents. The cycle of deprotectingthe prior amino acid and coupling the additional amino acid can berepeated until a peptide of the desired length is synthesized. Anyreactive side chains of the amino acids are typically protected bychemical groups that can withstand the coupling and α-amino deprotectionprocedure. These side chain protecting groups, however, can be removedat the end of the synthesis. Accordingly, each dispenser of asynthesizer of the present embodiments can be configured to dispense awash solution, deprotection reagent, amino acid, or activation reagent.The relative placement of the array of stations, relative placement ofthe array of reaction sites and the schedule by which the arrayscommunicate with each other can be correlated in accordance with theteachings herein and the known reaction schemes for peptide synthesisincluding, for example, those described in Goodman et al. (Eds.).Synthesis of Peptides and Peptidomimetics, Vol. E22a. Georg ThiemeVerlag, Stuttgart (2002).

Overview of Particular Synthesizer Embodiments

FIG. 1 is a diagram of one embodiment of a continuous polymersynthesizer 10. As shown, the synthesizer 10 includes a hexagonal base15 which supports a rotary table 20. The rotary table 20 is disposedwithin the base 10 such that it can be actuated to rotate about acentral axis. Located around the outer edge of the rotary table 20 are aseries of plate modules 500, each of which is configured to mount with aplate holder (not shown) that is designed to hold a multi-well plate.This configuration is explained in more detail below.

Of course, it should be realized that embodiments are not limited to anyparticular configuration of plate holder or multi-well plate. Forexample, any type of reaction site that is used within the continuouspolymer synthesizer is within the scope of the present embodiments. Suchreaction sites include, for example, wells of a multiwell plate such asa microtiter plate or filter bottom plate, Eppendorf tubes, substratesfor microarrays such as silicon chips or glass slides, and any of avariety of known substrates or containers for holding reactionsolutions. Those skilled in the art will recognize that embodimentsexemplified herein with regard to microtiter plates can be readilyadapted to other reaction sites.

For purposes of illustration, the present embodiments are exemplifiedherein with respect to the use of a rotary table as a stage thatsupports an array of reaction sites that move along a circular path.However, other stages or configurations are also useful so long as theyare capable of continuous synthesis in accordance with the presentembodiments set forth herein. For example, a stage can move reactionsites in a path having a linear shape or a curved shape that correspondsto all or a portion of a circle, ellipse or other shape. Typically, astage used in the present embodiments is configured to accept an arrayof reaction sites such that the sites are placed in a fixed order andfixed intervals relative to each other. Thus, the array of reactionsites can be moved such that the relative positions of the reactionsites in the array are not altered. However, if desired a stage used inthe present embodiments can be configured to allow movement ofindividual reaction sites such that the relative positions of the sitesin the array can be altered. Furthermore, a stage need not move and canbe static, for example, in embodiments where an array of stations ismoved instead.

As used herein, the term “continuous,” when used in reference tosynthesis of a plurality of molecules, means that the order of steps andtime interval between steps for synthesis of each molecule occursaccording to a reaction schedule and the schedule is unaltered bymanipulations occurring for the other molecules. The manipulations caninclude steps occurring according to a reaction schedule; steps utilizedto initiate or terminate a synthetic reaction, such as addition of areaction vessel to a synthetic device or removal of a reaction vesselfrom a synthetic device; passive steps such as maintaining reagents at areaction site during an incubation step; or steps that differ from areaction schedule such as premature removal of a reaction vessel for afailed synthetic reaction. Thus, even in the presence of an errorrequiring replacement of a reaction vessel, a system that continuouslysynthesizes a plurality of molecules can process reactions for the othermolecules in an uninterrupted fashion. Continuous synthesis should notbe interpreted to require continuous movement of any part of a system ofthe present embodiments. A continuous synthesizer may, for example, stopmoving as a rotary table changes direction and may do so whilecontinuous synthesis occurs at multi-well plates on the rotary table.

Accordingly, the present embodiments provide systems and methods whereinan array of reaction sites or an array of stations move on a schedulefor sequential communication of the reaction sites with the stations,wherein the relative locations of the stations and the schedulecorrelate with the order and duration of the sequential steps of aparticular reaction. As used herein, the term “steps of a reaction”means manipulations carried out or allowed to occur for a chemicaltransformation or change. The term “reaction schedule” means apre-defined order and duration of manipulations to be carried out for achemical transformation or change.

Returning to the exemplary synthesizer of FIG. 1, as the rotary table 20rotates within the base 15, the plate modules 500, which include plateholders (not shown) that are removably mounted to the rotary table 20,also rotate along the outer circumference of the rotary table 20. Fixedin position, and mounted to the top of the synthesizer 10 are a seriesof dispensers 35A-F and cameras 38A-E. This will be described morecompletely with reference to FIG. 2. It should be noted that as therotary table 20 moves about its central axis, each of the plate modules500 progressively move beneath the dispensers, also termed “dispensingstations” so that reaction solutions can be dispensed into themicrotiter plates. In one embodiment, the reaction solutions aredispensed by dispensing valves into the microtiter plates as the rotarytable 20 is moving. The dispensing valves are also termed “dispensingnozzles” and are typically static, whereby they do not move relative tothe dispensers during the course of reagent delivery in a syntheticcycle.

In the embodiment shown in FIG. 1, a feedback mechanism can be used thatdetermines the position of the rotary table in relation to the dispenservalves. Such a determination can be made continually throughoutoperation or at specific times such as following an adjustment made tothe system. In one embodiment, a sensor is used that determines theposition of a fiducial on a microtiter plate or other reaction site.Once the sensor has determined the position of the rotary table, thislocation information is fed back to the system that controls the rotorand the timing of the valves in the dispenser nozzles. In oneembodiment, the fiducial is a plastic structure, such as a rib or edgeof a well, in the microtiter plate. Additionally or alternatively, adetectable device or material can be temporarily used in place of areaction site, for example, being temporarily placed in a plate moduleon rotary table 20 during a calibration step.

In one embodiment, the rotary table 20 is configured to have a diameterthat is large enough so that the plate modules located along the outercircumference of the table follow an almost linear trajectory as theypass under each dispenser. For example, the rotary table shown in FIG. 2may have a diameter of about 77″ such that the microtiter plates locatedon the outer edge of the table follow a circular path that approximatesthe circumference of the table. As the diameter of the table increases,the path of the plates along the edge of the table become moreapparently linear with the increase in circumference. Accordingly, thediameter of a rotary table used in the present embodiments can beselected from sizes including at least about 77″, 80″, 85″, 90″, 100″ orlarger. It will be understood that smaller diameters can also be used,for example, in cases where fewer reaction sites are to be used, thediameter of a rotary table can be at least about 60″, 54″, 48″, 42″ or36″ or smaller. In embodiments wherein the reaction sites are not placedon the outer edge of the rotary table, those skilled in the art willrecognize that the diameters exemplified above, and the correspondingcircumferences, can apply to the dimensions of the circular path of thereaction sites.

The exemplary system shown in FIGS. 1 and 2 moves in a net clockwisedirection. However, the system can be configured to move in acounterclockwise direction as well. For example, reaction solutions canbe dispensed into a microtiter plate from a particular dispensingstation while the rotary table moves in a clockwise direction. Thedirection of movement for the rotary table can then be changed fromclockwise to counterclockwise direction. The counterclockwise distancetraveled by the table can be such that the microtiter plate is placed inposition to be imaged by one of the imaging stations 38A-E. Thedirection of the rotary table can again be changed whereby themicrotiter plate that was imaged is moved in a clockwise direction pastthe particular dispensing station to the next dispensing station. Themovement of the rotary table, although changing directions severaltimes, occurs such that the net movement is in a clockwise direction.Furthermore, continuous synthesis occurs at each microtiter plate(numbered 1 through 36 in FIG. 2) because the movement of the table andplacement of the stations allows all microtiter plates to receivereactants and incubate the reactants according the reaction scheme shownin FIG. 4.

It will be understood that a system of the present embodiments whetherusing a rotary table or other stage for accepting an array of reactionsites can move in two directions as exemplified above or in a singledirection as desired to suit a particular application of the system.Accordingly, an imaging station can be placed such that it is eitherbefore or after a particular dispensing station in the net path ofmovement for a system. An imaging station can be placed relative to thelocation of one or more of the dispensing stations and relative to themovement of the system so that an image of each reaction site can betaken after one or more reaction solutions has been dispensed.Particular embodiments of imaging stations useful in the presentembodiments will be described in more detail below.

It should be realized that image processing software running on an imageprocessing system can be configured to receive a copy of an image andthereafter determine if the proper solution was actually dispensed ineach reaction vessel. In one embodiment, the image processing systemdetermines if one or more of the wells in a microtiter plate is full orempty. In another embodiment, the image processing system can determinethe absorbance properties of the reaction solution within each well suchas the wavelength of light absorbed or the optical density at one ormore wavelength. The absorbance properties of a reaction solution in awell can be used to determine yield of a colorimetric reaction usingmethods set forth elsewhere herein or known in the art as described, forexample, in US Pat. App. Pub. No. 2004/0219063. If the image processingsoftware determines that the dispenser did not properly add a reactionsolution to a particular well of the microtiter plate or that a desiredlevel of color is not present, then that well or the plate containingthat well can be flagged as bad within a laboratory informationmanagement (LIMS) system that monitors the progress of the synthesisreactions occurring within the continuous synthesizer 10.

Those skilled in the art will recognize that an imaging station usefulin the present embodiments can be configured to detect any of a varietyof detectable characteristics of a reaction site such as an opticalproperty including, without limitation, absorbance, fluorescence,chemiluminescence, polarization, circular dichroism, fluorescenceresonance energy transfer (FRET), light scattering or the like.Furthermore, those skilled in the art will readily recognize that anoptical detection device, such as those set forth herein can be modifiedor replaced with any of a variety of known detection devices appropriatefor monitoring such optical properties. Further still, the presentembodiments can be used to detect changes in optical properties thatoccur in one or more range of the electromagnetic spectrum including,without limitation, infrared, visible, ultraviolet, x-ray, microwave,sub-regions thereof such as red, blue or yellow sub-regions of thevisible region, combinations of these regions or sub-regions, or otherregions of the spectrum.

An imaging station useful in the present embodiments can include acamera device such as a charge couple device (CCD) camera of the typeincluding, but not limited to, the AXIS 2100 Network Camera provided byAXIS Communications, Inc. of Lund, Sweden. One should appreciate thatother types of cameras may be used in accordance with the presentembodiments. A camera used in the present embodiments can be any devicethat converts a detectable optical property into a signal in a locationdependent manner. Thus, exemplary cameras useful in the presentembodiments include, for example, complementary metal oxidesemiconductor (CMOS) camera, video camera, internet camera, or otherimaging device capable of converting a picture into a digital image.Other imaging devices known in the art can also be used including, forexample, those described in US Pat. App. Pub. No. 2004/0219063.

As set forth above, the present embodiments include a synthesizer thatis capable of continuing to synthesize polymers within a multi-wellplate, even if one well within that plate has been determined to be bad.For example, if the imaging system determines that one well of amulti-well plate did not have a reaction solution added to it, then theentire multi-well plate need not be marked as bad. Rather the specificwell can be indicated as a failed synthesis. Thus, the system cancontinue to deliver solutions to other wells of the multi-well plate inorder to synthesize polymers therein while delivery of solutions to thefailed well is discontinued to avoid waste of reagents. Furthermore, itwill be understood that the synthesizer can continue to synthesizepolymers within other multi-well plates, even if one of the plateswithin the array of plates is identified as a failed plate becausesynthesis at the failed plate can be selectively discontinued or thefailed plate can be selectively removed from the rotary table withoutperturbing delivery or incubation of reagents at the other plates.

FIG. 2 is a schematic diagram of the rotary table 20 and dispensingstations 35A-F and imaging stations 38A-F useful in the presentembodiments. As shown, a load station 45 exists which is configured toallow plate holders to be loaded onto plate modules 500 on thesynthesizer 10. A load station can be configured for both loading andunloading of a multi-well plate or other reaction site or,alternatively, separate stations can be used for loading and unloadingof a reaction site from the system. The plate modules and theirassociated plate holders will be explained more specifically withreference to FIGS. 5A-D. It should be realized that plate holders, eachof which support a microtiter plate, can be loaded onto the synthesizer10 either manually or using an automated handling device such as arobotic arm. In addition, a unique bar code can be assigned to eachmicrotiter plate so that each plate can be automatically tracked fromthe time it is placed onto the synthesizer 10 until it is removed. Acomputer control system, as will be described hereinafter can monitorthe progress of each microtiter plate as it moves onto and off therotary plate, and thereby keep control over the reactions that are beingcarried out by the synthesizer at any one time. In one embodiment, a barcode scanner is associated with the automated handling device such thateach plate which is loaded or unloaded from the synthesizer 10 isscanned and tracked within a LIMS.

As shown in FIG. 2, the synthesizer 10 can be configured to manufactureoligonucleotides within microtiter plates or other multi-reaction sitesubstrate. Each well of the microtiter plate is assigned a differentoligonucleotide to be synthesized based on predetermined requirements.Based on this assignment, a LIMS, as described below, instructs eachdispenser to output the proper reaction solutions into the proper well.Each dispenser includes one or more valves, each of which is configuredto accurately dispense reaction solutions into a microtiter well.

Once a plate holder is loaded onto a plate module 500 on the rotarytable 20, the plate module enters below the wash station dispenser 35A.As the plate module enters below the dispenser 35A, the valves withinthe dispenser 35A output a wash solution into the microtiter wells. Inone embodiment, the dispenser includes 24 individually controlled valveswhich are configured to dispense wash solution into 24 wells of amicrotiter plate. As shown in FIG. 8, the dispensing nozzles can beconfigured to match the pattern of wells in one or more rows or columnsof a 384 well microtiter plate 515. As the microtiter plate passes belowthe wash dispenser 35A, each valve is timed to release a predeterminedquantity of wash solution into each well of the microtiter plate. In oneembodiment, the wash solution is an acetonitrile (ACN) wash solution.The number of dispensing nozzles utilized at a wash station or othersolution dispensing station can be fewer than the number of reactionsites. By way of illustration, the system exemplified above as having 24valves can deliver solution to all of the 384 wells of the microtiterplate if each of the 24 valves fires 16 times, thereby filling all 16rows of the microtiter plate. Thus, a dispensing station can have asingle linear arrangement of valves, for example, corresponding to asingle row or column of a microtiter plate, or multiple lineararrangements of valves that form a matrix of rows and columnscorresponding to all or a portion of the wells in a microtiter plate.

After a wash solution is dispensed into each well, and it has beenallowed to incubate for a desired time, the solution can be removedusing a solution removal device such as a vacuum source. In oneembodiment, the vacuum source is in continuous communication with theplate modules as the rotary table rotates. A valve can be placed betweenthe vacuum source and plate for attenuated communication between thevacuum source and the plate. The vacuum acts as a solution removaldevice to remove solutions from the microtiter plate. In thisembodiment, the microtiter plate is a “filter bottom” type plate whereinthe bottom of the microtiter plate is liquid permeable. Filter bottommicrotiter plates are available, for example, from Innovative Microplate(Chicopee, Mass.—innovativemicroplate.com). Typically, a growingoligonucleotide is covalently attached to the well or to a solidsubstrate such that it does not pass through the filter. Thus, thegrowing oligonucleotide is retained in the well upon application of avacuum. Those skilled in the art will recognize that other substrateshaving reaction sites capable of vacuum evacuation, such as filter disksor chips, can similarly be used in the present embodiments.

In the above-described embodiments, a single vacuum source can beconnected to the multi-well plates. For example, a vacuum pump can beplaced at a location away from the rotary table and in communicationwith the plates via a rotary union with an electrical slip ring. Asshown in FIG. 2, a series of vacuum lines 48A-G can run from a centralorifice 50 of the rotary table 20 and connect to each plate module 500.For illustrative purposes, only a subset of the vacuum lines are shownin FIG. 2, but it will be understood that each of the multi-well platesof the array can be in communication with a vacuum source via a vacuumline. The rotary union allows a vacuum line to communicate with each ofthe multiwell plates and to travel with each of the multiwell plateswhile the rotor is moving and while the vacuum source is maintained at astatic location.

In particular embodiments, the vacuum supply to each multi-well platecan be controlled by separate valves. For example, an electrical slipring of the rotary union can contain a series of electrical circuitswhose contacts move relative to one another but maintain continuity asthe device rotates, thereby allowing operating solenoids to travel witheach of the multi-well plates. By connecting a solenoid valve to each ofthe moving plates, the vacuum to each plate can be turned on or off bythe system at any time during the synthesis cycle. This configurationprovides the advantage of keeping the instrument compact, minimizingmechanical complexity and contributing to high reliability. Furtherdescription of plate modules and configurations of the plate modulesrelating to interaction with a vacuum source and multiwell plate are setforth below.

It should be realized that prior to evacuation of the ACN wash, an imageof the multi-well plate can be taken by one of the digital cameradevices, and thereafter sent for processing to the image processingsystem. The image processing system can analyze the image, as discussedbelow, to determine if each well of the microtiter plate was properlytreated with a wash. If a well is not found to have a wash solution,then that well can be marked as bad, or can be marked to be treated withan additional wash at a later cycle. The image processing system can beused in a similar fashion to determine if solution has been sufficientlyremoved from a multi-well plate based on an image acquired after anevacuation step.

Following the wash step, the plate modules can move to a position underthe deblock dispenser 35B. This dispenser is configured to dispense adeblocking solution containing, in one embodiment, trichloroacetic acidthat reacts with the growing oligonucleotide to remove a dimethoxytrityl(DMT) group from the last nucleotide. Removal of the DMT group from anoligonucleotide allows the addition of a subsequent nucleotide to thegrowing polymer chain. The release of DMT is readily identifiable by abright orange color that can be imaged by one of the cameras of thesystem. Accordingly, once the deblocking step has occurred, the platemodule can rotate under another camera which images the reaction sitesand thereby determines whether the deblocking step was successful bymeasuring whether each reaction solution has a bright orange color. Theoptical density of the orange color at each reaction site can bedetermined from the image and used to evaluate coupling efficiency,yield or other characteristics for each individual synthetic reaction.The plate module can then be evacuated to remove the deblockingsolution.

The plate module can then be moved under a washing dispenser 35D whichis configured to wash any additional deblocking solution from each well.The system can take an image after the addition of a wash solution todetermine whether or not each well received the washing solution andthereafter the wash solution can be evacuated from each well.Acetonitrile (ACN), an inert solvent, is used for this and other washsolutions in the protocol in one embodiment.

After being washed at the dispenser 35D, the plate module travels underthe coupling dispenser 35E wherein the appropriate nucleotide is addedto each of the wells. As can be imagined, if the next nucleotide in anoligonucleotide is an “A”, then the dispenser 35E would dispense asolution of adenosine into the well. The dispenser 35E is configured todispense the proper nucleotide into each of the wells of the microtiterplate within the plate module. Of course, the system can be configuredso that there are multiple dispensers, wherein each dispenser isconfigured to provide a different nucleotide to each well. Furthermore,a system of the present embodiments can include one or more dispensingstations that are configured to deliver modified nucleotides. Separatestations or dispensing nozzles can be used to deliver modifiednucleotides in a dedicated fashion. Alternatively, a station ordispensing nozzle can be configured to deliver a plurality of differentnucleotides, 2 or more nucleotides having naturally occurring bases ofA, T, C, G or U, or modified a version of these and other nucleotides.

Following delivery from the coupling dispenser 35D, the plate module canpass under another camera that takes an image of the microtiter plate toensure that a nucleotide solution has been administered to appropriatewells. The liquid contents of the plate can then be evacuated, wherebythe nucleotide solution is removed from the growing polymer.

The plate module can then move to an oxidation dispenser 35G. Thisdispenser disperses an oxidation reaction solution, containing iodine,into appropriate wells as the next step in the reaction process. Thissolution can then be imaged and evacuated, and the plate module moved toa cap dispenser 35H for the final stage in the oligonucleotide synthesisreaction. Once the cap solution, which contains acetic anhydrideactivated with N-methylimidazole, is dispensed into appropriate wells,the plate can continue on its circular path. If the reaction iscompleted, then the plate module can be removed at the load/unloadstation 45 located just after the cap dispenser 35H. If synthesis ofoligonucleotides in the plate is not complete, the plate module can makea further lap under the array of dispensing stations for addition ofanother nucleotide to the growing oligonucleotides in the multi-wellplates.

Those skilled in the art will recognize that the order by which themicrotiter plate communicates with different stations set forth above isprovided for purposes of illustration. The order in which a reactionsite communicates with separate stations, direction of relative movementbetween a reaction site and array of stations, and duration betweenreaction site manipulations can be selected to suit a particularreaction or application of the present embodiments and can, therefore,differ from that exemplified above.

Accordingly, one embodiment is a system for continuously synthesizingmolecules, whereby the molecules are synthesized by performingsequential steps of a reaction. In one embodiment the molecules areoligonucleotides or polypeptides. In this embodiment, the systemincludes a stage configured to accept an array of reaction sites. Areaction site may be, for example, a filter bottom microtiter plate, atube, or any other means for holding reaction solutions. The system alsoincludes an array of different stations. One set of stations are reagentdispensing stations, such as the dispensers 35. These stations areconfigured to separately and sequentially provide synthesis reactionsolutions to the reaction sites for carrying out the sequential reactionsteps. In addition, the array of stations can be configured in a fixedspatial relationship corresponding to the order of the sequential stepsof the reaction

Another set of stations that can be included in an array of stationsincludes imaging stations that are configured to obtain images of thereaction sites either after reactions solutions have been dispensed, orafter the solutions have been evacuated. The system can also include acontrol system, as discussed below, that is configured to move the stageor the array of stations so that the reaction sites sequentiallycommunicate with the dispensing stations and the imaging stations. Thisallows the dispensing stations to dispense reaction solutions to thesites, and the imaging stations to image the sites. In one embodiment,the control system is further configured to allow replacement of a firstreaction site, such as a microtiter plate, from the array of reactionsites with a second reaction site while the system continuouslysynthesizes molecules at other reaction sites of the array of reactionsites.

It should also be realized that the system can also monitor the qualityor yield of a synthesis reaction, and not just whether or not thereaction has occurred. For example, the continuous synthesizer can beconfigured for use in monitoring parallel chemical reactions and isparticularly suited for real-time monitoring of polymer synthesis suchas oligonucleotide synthesis or peptide synthesis. The synthesizer isalso particularly suited for providing a quality control (QC) measurefor oligonucleotide, peptide or other polymer productions. In oneembodiment, the chemical reaction monitor is an automated DMT monitoringsystem used to track the yield, quality and general state ofoligonucleotides being synthesized at any one time. Although the presentembodiments are exemplified herein in the context of oligonucleotidesynthesis one should appreciate that the chemical reaction monitor ofthe present embodiments is not limited to oligonucleotide synthesis andmay be used in the monitoring of other types of chemical reactions.Further examples of methods for detecting the quality of a synthesisreaction can be found in WO 04/065000 and US Pat. App. Pub. No.2004/0219063, the entireties of which are hereby incorporated byreference.

A method or system of the present embodiments can be used forsimultaneous synthesis of a large number of reactions. For example, thesystem exemplified in FIG. 2 includes 36 plates each having 96 or 384wells, thereby being capable of simultaneously carrying out 3,456 or13,828 individual reactions, respectively, at any given time. Thoseskilled in the art will recognize that the system can be configured tocarry out larger numbers of simultaneous reactions, for example, byincreasing the number of multi-well plates used or the number of wellsin each plate or both. Similarly, a system of the present embodimentscan be configured to carry out fewer simultaneous reactions, forexample, by using fewer multi-well plates or fewer wells per plate.Accordingly, a system or method of the present embodiments can beconfigured for continuously carrying out at least about 100, 1×10³,1×10⁴, 1×10⁵ or 1×10⁶ reactions simultaneously.

Continuous synthesis using a system or method of the present embodimentsprovides for high-throughput production of desired products. Forexample, the system exemplified in FIG. 2 can operate at a rate thatallows each 384-well plate to complete one lap in 9 minutes. However,because the system is continuously performing nucleotide additionreactions in 36 plates, the system will complete 13,824 (=384×36)nucleotide addition reactions in 9 minutes. This works out to 92,160nucleotide addition reactions completed per hour. Depending upon thereaction conditions selected, the present embodiments can be used tocomplete a synthetic cycle, such as addition of monomeric units togrowing polymer, in at least about 1, 5, 7, 8, 9, 10, 11, 12, 15, 20,30, or 60 minutes. This rate of synthesis can apply to any of a varietyof numbers of reaction sites, such as those exemplified above.Generally, throughput using the present embodiments, depending uponreaction conditions selected, can be, for example, at least about 100,500, 1×10³, 5×10³, 1×10⁴, 5×10⁴, 1×10⁵, 5×10⁵ or 1×10⁶ reactions orreaction cycles completed per hour.

Exemplary Continuous Polymer Synthesis System

FIG. 3 is a block diagram of an exemplary continuous polymer synthesissystem 100 that includes the continuous synthesizer 10 linked through anelectronic connection 105 to a servo controller system 110. The servocontroller system 110 controls the servo 108 that is mounted below therotary table 20 and controls the precise position of the rotary table 20with respect to the dispensers and cameras.

A feedback line 112 keeps the servo controller system 110 in constantcommunication with the synthesizer 10 so that it maintains the positionof the rotary table in real-time. A position sensor 115 detects theposition of the microtiter plates as they move around the rotary table,and provides electronic feedback to the servo controller system 100. Theservo controller system 110 provides instructions to the servo 108 tomove the rotary table 20 to a particular position. In one embodiment,the sensor is a single beam sensor such as the Keyence LV-21A, LV-H35Fsensor. The position sensor 115 is configured to read markings on themicrotiter plates, or other portions of the rotary table, in order toconfirm that the table moves to its expected position. Additionally, theposition sensor 115 can provide feedback that is thereafter used by theservo control system 110 to mark the position of the plate relative tothe position of the rotary table such that the microtiter plates becomeproperly positioned under each dispenser. Those skilled in the art willrecognize that a similar feedback system can be used to calibrate thepositions of other reaction sites in a system of the present embodimentsand can be readily adapted to embodiments wherein the array of reactionsites, the array of stations or both are capable of motion. Furthermore,the feedback system can be used continuously during operation of asystem of the present embodiments or at particular times such asfollowing synthesizer construction or maintenance.

FIG. 6 provides an image of a microtiter plate 120 and shows a set ofalignment ribs 122A, B and C. These ribs are standard structures withina microtiter plate 120, and are therefore at the same position relativeto microtiter wells 124 within each microtiter plate in the system.Thus, sensors 115A,B can be used to determine the position of themicrotiter plate, and thereby the wells, as they rotate around thesynthesizer based on the location of the alignment ribs. Each sensor115A,B can be configured to detect when one of the ribs passes by thesensor as the microtiter plate 120 moves on the rotary plate. Thisinformation can be used to send feedback signals though the feedbackline 112 of FIG. 3. In cases where alignment is incorrect, appropriateinstructions can be sent by the system to reagent delivery stations orto a human user to improve alignment between the microtiter plate anddispensing nozzles. Such alignment can include change in physicallocation or adjustment in the timing of solution delivery from one ormore dispensing nozzles

Referring back to FIG. 3, the controller 110 is linked to an embeddedcontrol layer (TwinCat 130) that includes a programmable soft PLCrunning on a Windows XP compatible PC architecture. This system providesdeterministic control over the synthesizer hardware via the DeviceNetmodule 120 and LightBus control networks. The Soft PLC communicates withand controls the servo controller via the DeviceNet network.

The control system 150 contains software modules that communicate withthe synthesizer 10 and provide instructions concerning which well to adda particular nucleotide into, and which well should be given a modifiedbase. As can be understood, the control system 150 includes datarepresenting the proper oligonucleotides to be manufactured by thesynthesizer 10. These instructions are provided to the synthesizer 10 sothat it can properly actuate the dispensers at the proper time as eachwell of a microtiter plate passes under a dispenser. This allows thesystem to manufacture different oligonucleotides within each well of amicrotiter plate.

As set forth above, the control system 150 includes a storage devicethat stores oligonucleotide orders which specify the sequence ofoligonucleotides to be manufactured. When a new plate is loaded onto thesynthesizer 10, the control system notes the bar code number of thatplate and then associates that bar code with a particular order storedwithin the control system. The selected plate is then assignedoligonucleotide sequences that are to be synthesized within each well.The control system tracks each microtiter plate on the synthesizer, andcontrols the nucleoside bases which are deposited into each well duringsynthesis. Thus, during one cycle around the synthesizer 10, some of thewells may receive a “C” base, whereas other wells may receive an “A”,“T”, “G” or specially modified base depending on the sequence of theoligonucleotide that is to be synthesized within each well.

Control system 150 can provide instructions to dispenser stations 35A-Fvia the TwinCat control layer in the form of a firing table that isderived from a correlation of desired nucleotide sequences with thesynthesizer protocol. Nucleotide sequences can be imported into thecontrol system in the form of batch files listing the sequence for theoligonucleotide to be synthesized in each well. Batch files can beobtained from a variety of sources including, for example, direct inputfrom a user via a graphical user interface or via importation from acustomer order system such as the oligonucleotide ordering systemsdescribed in U.S. Provisional App. No. 60/634,164, which is herebyincorporated by reference in its entirety.

Each well in a batch file can be identified according to a barcode for aparticular plate and according to the location of the well in the plate(i.e. row and column). Using the example of the system shown in FIGS. 1through 4, the synthesizer protocol includes the location of eachmulti-well plate 30 on the rotary table 20, the location of thedispenser stations 35A-F and the rotation schedule of the rotary table20. For purposes of illustration, the schedule can be represented as aseries of “tics”, whereby each tic represents movement of the rotarytable 20 a discrete distance. Accordingly, a different set of wells willpass under a dispensing station during each tic. For each tic, thecontrol system provides a different firing table based on the identityof the wells and the sequences of the oligonucleotides to be synthesizedin the wells.

The firing table will be described in further detail with reference tothe screen shot provided in FIG. 10. The screen shot represents a userinterface for creating or modifying a firing table. In the screen shotand under the Delivery Parameters window, input options available foreach well are listed in columns. The input options listed includeactivated nucleotides (A, C, T and G), modification reagents (AmC6, HMDAand Phos), wash solutions (ACN, ACN Em, initial wash, and prebase) andvarious other reaction solutions (CAP, Deblock and Oxidizer). Outputreagents are listed in rows under the Delivery Parameters window. Thenumbers in the table correspond to the volumes of each reagent to bedelivered by the output device to satisfy the input option selected.

Several of the input options have multiple output options and aretherefore represented by aliases. An alias acts as a place holderrepresenting several different sets of instructions, wherein each set isbased on the specific reagents to be added for a particular synthesiscycle. For example, in a case where different initial wash treatmentsare used in connection with different modification steps, an alias forthe initial wash step can represent a first set of instructions to beused in a synthesis cycle when a first modification reagent is to beused and a different set of instructions when a second modification isto be used. Thus, appropriate initial wash instructions can be includedin a firing table based on the identification of a specific well andidentification of the modification to be made to the oligonucleotideassigned to the well. The firing table can be sent to the initial washdispenser 35A in response to the tic that brings the specific well intocommunication with dispenser 35A at the cycle in which the modificationis to be made to the oligonucleotide.

Two or more input options can be organized into groups. Several groupsare listed in the lower left window of the screen shot in FIG. 10including Activator and Mods, Bases and Bulk ACN. As shown in thescreenshot the Activator and Mods group is selected and includes theAmC6, HMDA and Phos input options. Organization of input options intogroups provides the advantage of convenient construction or modificationof firing tables. For example, a global change to be made for severalinput options can be readily made and/or visualized when the inputoptions are organized into a group.

Those skilled in the art will know or be able to determine appropriateinstructions for any of a variety of reactions based on the exemplarycontrol system described above. For example, any of a variety ofpolymers or other products of repetitive reaction cycles can besynthesized using a firing table listing reactive solutions suitable forthe particular reaction of interest. However while embodiments describesynthesizing polymers, aspects of the present embodiments also includeassays such as determining the sequence of polymers. In one example, thesequence of DNA or proteins can be determined. Furthermore, the controlsystem exemplified for a rotary table-based instrument can be readilyadapted to other instruments such as those described elsewhere herein.Furthermore, instructions can be provided in other formats besides afiring table including for example, an electronic spreadsheet (forexample, EXCEL™ spreadsheet from Microsoft) a database table or any of avariety of formats that can represent text in an electronic file.

As shown, the control system 150 is also linked to an image server160A,B which is configured to process all of the images being capturedby the cameras 38 mounted around the synthesizer 10. In one embodiment,each camera device is a charge couple device (CCD) camera of the typeincluding, but not limited to, the AXIS 2100 Network Camera provided byAXIS Communications, Inc. of Lund Sweden. One should appreciate thatother types of cameras may be used in accordance with the presentembodiments. A camera used in the present embodiments can be any devicethat converts a detectable optical property into a signal in a locationdependent manner. Thus, exemplary cameras useful in the presentembodiments include, for example, a complementary metal oxidesemiconductor (CMOS) camera, video camera, internet camera, or otherimaging devices capable of converting a picture into a digital imagesuch as those set forth previously herein and in U.S. Pat. App. Pub. No.2004/0219063.

As discussed previously, each camera can be positioned on thesynthesizer 10 over a multi-well plate or other plurality of wells suchthat it is capable of obtaining an image which includes all of the wellsof a multi-well, or microtiter plate. The multi-well plate generallyincludes 96 or 384 wells, however, one should appreciate that themulti-well plate may include other numbers of wells such as more than384 wells. Advantageously, the camera device not only allows observationof the multi-well plate as a whole, but also allows observation of eachwell individually. In one embodiment, the camera incorporates an opticalfiltering stage rendering the detector capable of spectral measurementsand tunable to specific chemicals that exhibit specific absorptivitiesin the spectrum. An optical filter useful in the present embodiments canbe any device for selectively passing or rejecting passage of radiationin a wavelength, polarization or frequency dependent manner.

As illustrated in FIG. 3, the camera can transfer an imageelectronically to a storage location, such as the image servers 160A,B.In the exemplary embodiment shown in FIG. 3, the control system 150 isconfigured to control each of the cameras. For example, image controlsoftware may be configured to signal the camera device, via the centralnetwork, when to take an image of a multi-well plate of theoligonucleotide synthesizer 10. The image may be transferred to theimage process servers 160A,B in the form of a JPEG, TIFF, BMP file orother suitable file format. An exemplary example of an image of amicrotiter plate is shown in FIG. 6.

In particular embodiments, the image files are named according to batchnumber, plate number, or cycle number within the synthesis protocol thatthe synthesis process is at when the image is taken. In this respect,the term “cycle” refers to the complete cycle of steps for the additionof each base to the growing DNA chain including, without limitation, thedeprotection, coupling, capping, and oxidation steps. It will beunderstood that an operation can be performed one or several timeswithin the same cycle. Any of the steps set forth herein or otherwiseuseful in the present embodiments can be carried out as one or morerepetitions of the particular step. For example, the deprotection stepmay repeat two or three times within the same cycle whereby a repetitiondesignation can be used to differentiate the particular deprotectionoperation within a cycle.

FIG. 9 is a flow diagram showing one embodiment of a method 1000 forcontinuously synthesizing molecules. The method 1000 begins at a startstate 1002 and then moves to a state 1004 wherein reagents are dispensedfrom dispensing valves into a microtiter plate as the plate rotates on arotary table. After all wells of the microtiter plate have passed underthe dispenser valve, the microtiter plate moves below a camera so thatan image is taken at a state 1006. The microtiter plate can beilluminated with a light source such as an LED array. The camera can beplaced directly above the rotary table and the LED array can be placedto cast light in a direction towards the light path between the plateand camera such that the two light paths intersect. A beam splitter canbe placed between the camera and plate at the intersection point and ina configuration, whereby light emitted from the LED is reflected to theplate by the reflective side of the beam splitter and whereby the cameraobtains an image of the lighted plate through the transparent side ofthe mirror. One exemplary image can be found with reference to FIG. 6.Further description of imaging systems useful in the present embodimentsand appropriate configurations are described in U.S. Pat. App. Pub. No.2004/0219063.

Once an image of the microtiter plate has been taken, it is compared toa database of sequence data at a state 1010 to determine whether eachwell of the microtiter plate that was supposed to have received areagent is found to be filled. A file contained in the database and usedfor the comparison can include an expected property for a well based onthe presence or absence of a particular volume of liquid. For example,the file can provide a numerical scale ranging from an arbitrary darkvalue (for example, 4096) to an arbitrary bright value (for example, 0).The values can be assigned for a well based on one or more calibrationimages obtained for a plate that has been evacuated of solution, thatcontains an optically clear solution and/or that contains an opticallydense solution. In regard to the example of a scale from 0 to 4096, anevacuated well can have a value or range of values near 4096, a wellcontaining trityl can have a value or range of values near 0 and a wellcontaining an optically clear solution can have a value or range ofvalues between those for the emptied or trityl containing well. Theranges of values can be contiguous or alternatively can have gapsbetween them. The optical density can be measured for a plate duringsynthesis and its optical density compared to the numerical scale todetermine if it falls in the range of an empty, full, or tritylcontaining well. If the comparison results in a desired range, forexample, an evacuated well has an optical density in the range near4096, then synthesis for the well is allowed to proceed. If thecomparison results in a range that is outside of the desired range, forexample, occurring in a gap or in the range near 0, an error can beindicated and synthesis to the well discontinued.

For the above-described images, the optical densities can be determinedfor the center of a well or for a specific portion of a well such as acentral region of the well. Typically, the location of wells isregistered such that any image used for determining optical densityexcludes the edges of wells. Furthermore, individual wells are typicallycalibrated and compared on an individual basis to compensate fordifferent lighting effects at different parts of the plate. Althoughimage comparison is described above with respect to optical density, itwill be understood that other values can be used in a comparison file inplace of optical density such as the standard deviation for thedistribution of optical densities measured in a region of a well or theskew for the distribution.

The process 1000 then moves to a decision state 1012 wherein adetermination is made whether any errors occurred following comparisonof the image to the database. Such an error may be that a well that wassupposed to have received a reagent is not found to have a reagentwithin that well. Another error may be that a well that is supposed tobe empty is found to be filled with a reagent solution. If an error hasbeen found then process 1000 moves to a state 1016 wherein the error isreported back to the main system for further processing. The furtherprocessing may be, for example, that this well is marked as bad and thusdoes not receive further reaction solutions while the remaining wells inthe microtiter plate are completed. Additionally, the entire microtiterplate can be marked as bad and the system thereafter instructed to loada new microtiter plate onto the continuous synthesizer in order to carryout the reactions that were to occur in the bad microtiter plate.Alternatively or additionally a written or displayed report can also beproduced for the user of the system in order to notify the user thatsuch an error has occurred. Once the error has been reported at thestate 1016 the process 1000 terminates at an end state 1020.

However, if an error did not occur at the decision state 1012 then theprocess 1000 evacuates the microtiter plate at a state 1024 andthereafter takes another image at a state 1026 in order to determinewhether each well has been properly evacuated. At a state 1028 the imagetaken of the evacuated multi-well plate is compared to a database.

The process 1000 then determines whether any errors occurred at adecision state 1030 and if an error did occur the process returns to theerror reporting state 1016. However, if no errors occurred then theprocess moves to a decision state 1032 to determine whether thesynthesis reactions within the plate have been completed. If they havebeen completed then the process terminates at the end state 1020.However if the synthesis reactions within the plate have not beencompleted at the decision state 1032 the process 1000 returns to thestate 1004 to dispense additional reagents into the plate in order tocontinue the synthesis reactions.

Exemplary Oligonucleotide Synthesis Embodiments

FIG. 4 is a flow diagram illustrating an exemplary method 400 forsynthesizing oligonucleotides. The method begins at a state 410 whereina universal support is provided which is used as the anchor for theoligonucleotide. In one embodiment, the universal support is a universalcontrolled pore glass (CPG) substrate that is configured to be used toinitially anchor any nucleoside. One such universal CPG is availablefrom Proligo Reagents (Boulder, Colo.). Once the universal support isprovided, typically within wells of a filter-bottom microtiter plate,the process 400 moves to a state 412 wherein acetonitrile (ACN) is usedto wash the universal supports. Each well is then evacuated at a state414 such that wash solution is removed while the universal support isretained in the well. A deblocking solution, containing trichloroaceticacid, is then delivered to each of the wells at a state 418.

A determination is then made at decision state 420 whether or not anAmC6 modification is to be added to the oligonucleotide beingsynthesized. If an AmC6 modification is to be added, then the method 400incubates the deblocking solution for 180 seconds. If there is no AmC6modification, then the method 400 incubates the blocking solution for 45seconds. The deblocking solution is then evacuated at a state 428 andthe method 400 returns to state 418 to cycle one more time through theaddition of the deblocking solution. Once the method 400 has performedan additional cycle, another wash of ACN is performed at a state 430,followed by an evacuation at a state 432, and then a repeat of the ACNwash.

A determination is then made at a decision state 436 whether or not theoligonucleotide synthesis is finished. If the oligonucleotide is donebeing synthesized, then it is marked for completion at a state 437 andthe method 400 terminates. However, if the oligonucleotide synthesis isnot complete, then a determination is made at a decision state 438whether or not the oligonucleotide is to include a modification to the5′ end added by phosphoroamidite type chemistry or another alternativemethod.

If a decision is made that the oligonucleotide is to be modified at its5′ end using phosphoroamidite type chemistry then the process 400 loadsany nucleotide modifications at a state 440 and then delivers thosenucleotide bases to the reaction sites at a state 442. For example, ifan oligonucleotide is to be modified to include an amino group at the 5′end then monomethoxytritylaminohexyl phosphoramidite (MMT 5′ C6 Aminolinker available as cat. # C-1001 from Trilink, San Diego Calif.) can beloaded and delivered. A decision is then made whether any specialmodifications are necessary at a decision state 446 wherein if nomodifications are necessary the synthesizer incubates theoligonucleotides for sixty seconds, whereas if special modificationshave been delivered then the reactions are incubated for the appropriateperiod of time based on the type of modification that was introduced atthe state 440.

The microtiter wells are then evacuated at a state 448 and an oxidizersolution is delivered at a state 450. The oligonucleotides are thenincubated for fifteen seconds and each well is evacuated at a state 454in order to remove the oxidizer solution.

At a state 456 the process 400 delivers the capping solution to each ofthe wells and then incubates for approximately fifteen seconds. Thecapping solution is then evacuated at a state 458 and the process 400returns to the state 412 wherein an acetonitrile wash solution isintroduced into each of the wells.

It should be realized that if a determination was made at the decisionstate 438 that 5′ modification is to be carried out by a differentmethod than the phosphoramidite method set forth above, then the process400 moves to a state 460 wherein the alternative method is carried out.Upon completion of the alternative method, the oligonucleotide is thenremoved at the state 437.

Of course it should be realized that the synthesis process 400 is onlyone exemplary method for synthesizing oligonucleotides using thecontinuous synthesizer 10. Other synthesis reactions and conditions arealso contemplated to be within the scope of the present embodiments.Those skilled in the art will recognize that different reactionsolutions, reaction times, or sequences of reactions can be adapted foruse in the present embodiments, for example, by providing an appropriatespatial and temporal relationship between an array of reaction sites andarray of stations moving relative to each other in accordance with theteachings herein.

Exemplary Plate Module

FIG. 5A illustrates an exemplary plate module system 500 that includesan overflow tray 505 configured to hold a plate holder 510. Asillustrated, the plate holder 510 is designed to hold a microtiter plate515 so that it can be easily loaded and unloaded from the synthesizer10. The overflow tray 505 is generally rectangular in shape and includesa front edge 512, a rear edge 514, a left edge 516 and a right edge 518.A central surface 520 of the overflow tray 505 is configured to hold theplate holder 510. In use, the overflow tray 505 is mounted to the rotarytable 20 and provides the means by which the plate holder 510 is loadedand unloaded onto the synthesizer. In one embodiment, the plate holderis deposited or removed from the plate module while the rotary table isturning. This allows the synthesizer to continuously synthesize even asthe plate holders are being loaded and unloaded from the synthesizer

As can be envisioned, a filter-bottom microtiter plate is first securedinto a plate holder. The plate holder is then manually, orautomatically, loaded onto the synthesizer by placing the plate holderinto an overflow tray. The plate module, which is fixed to the rotarytable, then rotates around the synthesizer as the rotary table turns.

As shown, the plate holder 510 rests in the central surface 520 of theoverflow tray 505. The configuration of the plate holder 510 will beexplained more completely with reference to FIG. 5B. As illustrated, avacuum line 525 and a nitrogen line 528 enter the overflow tray 505through the rear edge 514. The vacuum line 525 runs inside the overflowtray 505 and communicates with a vacuum interface 530 in the centralsurface 520 of the plate module. When the plate holder 510 is properlyplaced onto the overflow tray 505, the vacuum interface 530 provides asource of vacuum for removing reaction solutions such as wash solutionsor reagent containing solutions from the filter-bottom microtiter platethat is housed within the plate holder 510.

The nitrogen line 528 communicates with a nitrogen knife 534 attached tothe rear edge 514 of the overflow tray 505. As illustrated, the nitrogenknife 534 includes a longitudinal opening 536 which is configured tooutput a generally flat sheet of nitrogen gas which layers over themicrotiter plate 515 within the plate holder 510. In one embodiment, thenitrogen gas acts to quarantine the reaction solutions from the ambientenvironment and also remove any vapor phase material from areasproximate to a reaction site. Also, when the vacuum line 525 isactivated to evacuate liquids from the microtiter plate 515, a layer ofnitrogen gas can be provided above the microtiter plate.

In one embodiment, the synthesizer outputs nitrogen gas at the same timethat the vacuum is actuated, thus pulling nitrogen gas into each well ofthe microtiter plate during the evacuation process. This preventsambient air or contaminants such as aerosolized reagents from beingforced into contact with reaction products while passing through thefilter bottoms of the wells. Because nitrogen is an inert gas, it ismuch less likely to cause a reaction with reaction products such aspolymeric molecules being synthesized within each well of the microtiterplate. Of course, it should be realized that the present embodiments arenot limited to only using nitrogen gas to overlay the microtiter plate.Any type of gas, preferably inert gas, such as argon or helium, is alsowithin the scope of the present embodiments. In an alternativeembodiment, a device similar to the quarantine devices described abovecan be used for delivery of a reactive gas to a reaction site in asystem of the present embodiments. Gas, either inert or reactive, canalso be provided by one or more stationary stations, such as dispensingstations or imaging stations such that when the plates are evacuatedthey ingest this gas preferentially over ambient air or pollutants. Forexample, imaging stations 38A-F can include a plenum between an upperwindow for the detector and a microtiter plate below. The plenum can bepurged with nitrogen such that gas flows in a direction that issubstantially normal to the microtiter plate. The flow of nitrogen gascan provide the advantages of removing moisture and debris from thewindow as well as displacing harmful vapors to reduce unwanted contactof these vapors with reaction products when the microtiter plate isvacuum evacuated at the imaging station.

Referring now to FIG. 5B, the plate holder 510 includes an upper frame550 which is configured to lock with a lower portion 552 of the plateholder 510. Within the lower portion 552 is a recessed opening 556 whichis sized to hold the microtiter plate 515. Thus, when the frame 550 isclosed against the lower portion 552, the microtiter plate 515 is heldin place within the plate holder 510. A set of locks 558A,B reversiblylock the frame 550 against the lower portion 552. As shown, a circularvacuum interface 560 is located in the recessed opening 556 and providesa through-hole to the vacuum source within the plate module 505.

Referring now to FIG. 5C, the lower portion of the vacuum interface 560can be seen through the bottom lower portion 552 of the plate holder510. In addition, a set of three stacking pins 565A, B, C are providedin order to raise the lower portion of the plate holder 510 from thecentral surface of the overflow tray 505. In addition, a set ofalignment holes 568A, B are provided such that the plate module 510aligns correctly within the central opening 520 of the overflow tray505.

As shown in FIG. 5D, a set of alignment pins 570A, B are illustrated inthe central surface 520 and configured to mate with the alignment holes568A, B of the plate holder 510 (FIG. 5C). In addition, a vacuum suctionbellows 575 is shown protruding from the central surface 520 andconfigured to reversibly mate with the vacuum interface 560 of theoverflow tray 505.

As shown in FIG. 5E, a cross sectional view of the plate holder 510mated with the overflow tray 505, the vacuum section bellow 575reversibly mounts within the vacuum interface 560 so that the vacuumline 525 can evacuate reaction solutions from within the microtiterplate 515. The vacuum suction bellow 575 is preferably a flexiblepolymeric material, such as silicon or rubber, and is configured toprovide a quick and efficient reversible seal with the vacuum interface560. As illustrated, the vacuum suction bellows 575 includescompressible portions 580 which are adapted to compress or expand as theplate holder 510 is placed on top of the bellow 575.

As should be realized, when the plate holder 510 is placed onto theoverflow tray 505, the bellows 575 becomes recessed within the vacuuminterface 560 of the plate holder. The compressible portions 580 of thebellows allows the vacuum interface 560 of the plate holder to bedropped on top of the bellow, and thereafter have the compressibleportions 580 compress and create a vacuum tight seal between the plateholder 510 and the overflow tray 505.

In accordance with the embodiments set forth above, a module system ofthe present embodiments can be configured to provide the non-limitingadvantages of (1) convenient addition and removal of a first reactionsite without interrupting synthesis occurring for a second reactionsite, (2) providing a continuously available solution removal devicesuch as a valve attenuated vacuum source, and/or (3) providing acontinuously available quarantine device such as a valve attenuated gasknife. Those skilled in the art will recognize that a similar modulesystem can be used to hold a substrate for reaction sites having otherconfigurations including, for example, a multi-well plate having a shapeor number of wells that differs from the microtiter plate exemplifiedabove. Furthermore, a module system of the present embodiments can beconfigured for use with other reaction site substrates such as thosedescribed elsewhere herein. In embodiments including vacuum basedremoval of solutions, filter based substrates are particularly useful.

Exemplary Devices and Methods for Dispensing Liquids

Referring to FIG. 7, a diagram of an exemplary system 700 for providingreaction solutions to the dispenser 35A is illustrated. Within thedispenser 35A is a local reservoir 710 that hold the reaction solutionsthat are to be dispensed by the dispenser 35A. A set of level detectors715 are used to measure the level of the local reservoir and determinewhen it is time to pump more reaction solution from a storage tank 720.As shown, the storage tank 720 is connected to a helium source 722 whichis used to pressurize the storage tank 720. The helium pressure can beadjusted, for example, under computer control to force additionalreaction solution to the local reservoir 710 when the level detectors715 indicate that the local reservoir 710 is below a predeterminedthreshold.

By providing a local reservoir of reaction solutions, the system canprovide smoother and more reliable dispensing because the liquids do nothave to travel through long lines to reach each valve. Any gas pocketsor other small changes in pressure within one of such lines can lead toundesirable dispensing conditions, especially when the volumes to bedispensed are very small. In particular, use of a hydraulically coupledlocal reservoir can provide the advantage of eliminating pressurevariations that typically occur across a manifold that is connected tomultiple dispenser valves, such as the pressure variance that arises dueto differences in the number of valves that are open at any given timeand the pressure variances that are caused by the opening and closing ofvalves. Elimination of such effects using, for example, hydraulicallycoupled local reservoirs provides for staggered firing of individualdispenser nozzles wherein any number of valves can be actuated at anytime, as set forth below.

The local reservoir 710 is fluidly connected to a series of solenoidvalves 720 which are independently controlled by the control system 150to independently control fluid delivery from individual dispensernozzles. The control system 150 provides commands to the valves 720 todispense reaction solutions from the local reservoir 710 when wells 725of a microtiter plate 730 are properly aligned below each valve.

In particular embodiments, a system can be configured for staggereddispenser valve actuation such that staggered liquid dispensing occursfrom a set of dispenser nozzles. As reaction sites arrive at each of thedispenser stations, solenoid valves can control reagent dispensing. Eachreagent dispensing station can use multiple solenoid valves that arefired one at a time or in groups depending on the size of the powersupply utilized. The number of simultaneous valve actuations per reagentcan be constrained in order to limit the electrical current demand andtherefore the size of the power supplies, if desired.

A dispensing station can be configured to deliver a different volume offluid from different dispenser nozzles if desired. Alternatively oradditionally, each dispenser nozzle can be controlled to deliver fluidat different start times, for example, as set forth above. The abilityto dispense different volumes of fluid and to do so at different starttimes provides advantages over typical fixed volume or positivedisplacement type dispensers by allowing a high level of control overreagent utilization during a synthetic operation.

A valve dispenser useful in the present embodiments can be controlledusing a hardware abstraction layer (HAL) that fires valves and managesthe filling and pressurization of local reservoirs. Discrete logic canbe used, for example, via a complex programmable logic device (CPLD), toimplement a finite state machine for the local reservoir filling and togenerate spike and hold signals that control the valves. The discretelogic for each spike and hold circuit for each valve is typicallyseparate and independent of one another. This allows all valves to befired simultaneously, slightly staggered, or selectively such that oneor more are fired and others are not during a finite time period. Use ofa hardware abstraction layer to control a multi nozzle dispenserprovides advantages over the use of a microprocessor because a HAL canbe scaled to the use of larger numbers of nozzles without increases incost and computation time that can occur when a microprocessor is used.However, it will be understood that if desired a microprocessor can beused in the present embodiments, for example, in cases where arelatively small number of nozzles is to be controlled.

Exemplary logic for a HAL that is useful for controlling an individualvalve in a dispensing station of the present embodiments is shown in theform of the circuit diagram of FIG. 11. The circuit diagram exemplifiescontrol via two outputs including a spike output 915, which provides afirst voltage that is activated immediately and for a discrete timeperiod of a relatively short duration, and a hold output 914 whichprovides a second voltage that is activated after the spike output andis maintained for a discrete time period of a longer duration. Spikeoutput 915 is at a voltage sufficient to open the valve, whereas thehold output 914 is at a lower voltage, sufficient to maintain the valvein an open state. The HAL can receive four different inputs includinginputs 901, 902, 903 and 904. Input 901 is configured to receive a logic“high” signal received from an I/O interface and controls the valve inresponse to signals generated from a firing table. The signal from input901 is processed in accordance with the activities of other inputs viaOR gate 905 and multiplexer 907. The timing for the outputs iscontrolled by passage of the signal from OR gate 905 through an NANDgate 908, flip flops 909, 910 and 913, then OR gate 912 and back to ORgate 908. The clock cycle is selected to control duration of the spikeand hold outputs. For example, in the HAL diagram of FIG. 11 the spikeoutput 915 has a duration of 1 millisecond which corresponds to twoclock cycles. Input 902 is configured to allow manual firing of a valve,for example, via a switch that is connected to all valves in a dispenserdevice. Input 903 is configured to allow a signal to be sent to the HALfor the purpose of turning valve indicator LED's on or off to make adesired pattern, for example to communicate a message to a user. Input904 receives signals from a clock. Circuitry such as that shown in thediagram can be replicated ad-infinitum for as many valves as necessary.

A requirement for a relatively large amount of energy can arise shouldthe occasion of firing all valves simultaneously present itself to theHAL. In this case, enough current to source the spike of all of thevalves can be stored locally. Any of a variety of capacitors known inthe art can be used to store the current. Local storage of currentreduces the instantaneous demand for current on the power supply usedfor the dispenser, thereby providing advantages of reducing the cost ofthe power supply and reducing the amount of space required to house thepower supply. Thus, the HAL is typically configured to store at least anamount of energy sufficient to fire all of the valves simultaneously.

FIG. 8A shows a diagram of one embodiment of a dispenser 35A as it isoutputting solutions to a microtiter plate 515 simultaneously withmovement of the microtiter plate via the rotary table 20. As shown,within the dispenser 35A are a series of linear valve arrangements 805,810, 815, 820, 825, 830 and 835. Each linear arrangement of valves isfluidly connected to the same reagent solution reservoir and a differentreservoir delivers solution to each linear arrangement of valves. Forexample, the valve column 805 is connected to a modified nucleoside.Valve column 810 is connected to an adenosine solution, column 815 isconnected to a cytidine solution, column 820 is connected to a guanosinesolution and column 825 is connected to a thymidine solution. It will beunderstood that the sugar moiety for the nucleosides is typically adeoxyribose for synthesis of DNA. However, monomers can contain othermoieties such as ribose sugars useful for synthesizing RNA or moietiesused for synthesizing nucleic acids having alternative backbones such aspeptide nucleic acids (PNA). Columns 830 and 835 can be connected to,for example, ACN wash solutions, deblocking solutions or cappingsolutions depending on their position in the synthesizer. Of course itshould be realized that the number and type of valve-reservoirconnections used in the present embodiments can be altered from thoseexemplified above to suit a particular application. For example, eachdispenser may have only one valve column, or any other number of valvecolumns without departing from the spirit of the present embodiments. Inone embodiment, the valve columns are removable and interchangeable sothat a particular dispenser can be outfitted with any number of valvecolumns to dispense the correct solutions for synthesizing a polymer.

INCORPORATION BY REFERENCE

All references cited herein, including patents, patent applications,papers, text books, and the like, and the references cited therein, tothe extent that they are not already, are hereby incorporated herein byreference in their entirety.

Equivalents

The foregoing written specification is considered to be sufficient toenable one skilled in the art to practice the present embodiments. Theforegoing description and Examples detail certain preferred embodimentsand describe the best mode contemplated by the inventors. It will beappreciated, however, that no matter how detailed the foregoing mayappear in text, the present embodiments may be practiced in many waysand the present embodiments should be construed in accordance with theappended claims and any equivalents thereof.

The term “comprising” is intended herein to be open-ended, including notonly the recited elements, but further encompassing any additionalelements.

1. A method for continuously synthesizing molecules, comprising: (a)providing a stage comprising a plurality of reaction sites in a fixedorder and at fixed distances from one another, (b) providing a pluralityof dispensing stations configured to deliver reagents to said reactionsites to start a reaction, wherein said dispensing stations are locatedalong said stage at a fixed distances from one other and wherein saiddistances correlate to the time required to complete said reaction; and(c) sequentially dispensing said reagents into said reaction sites on apredetermined schedule so that a first reaction in a reaction site iscompleted before a second reaction in said reaction site is initiated,and wherein said distances and said schedule correlate to the order andthe duration of steps required to complete said reaction.
 2. The methodof claim 1, wherein said molecules comprise polymers.
 3. The system ofclaim 2, wherein sequentially dispensing said reagents comprisessequentially dispensing monomers to said polymers.
 4. The method ofclaim 1, wherein said stage comprises a circular table.
 5. The method ofclaim 4, wherein said dispensing stations are located along an outercircumference of said circular table.
 6. The method of claim 5, whereinsaid circular table rotates at a predetermined speed so that saidreaction sites move below said dispensing stations at a predeterminedtime.
 7. The method of claim 6, wherein said reaction sites move from afirst dispensing station to a second dispensing station, and saidpredetermined time is calculated so that said reaction is completedbefore said reaction site is positioned below said second dispensingstation.
 8. The method of claim 1, wherein said means for sequentiallydispensing said reagents comprises a control system.